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Bücher Englische Bücher Wissen & Bildung Naturwissenschaft, Medizin, Informatik, Technik Technik Luft- und Raumfahrttechnik Conceptual Design of Boundary Layer Suction System for Energy Efficient Laminar Flow Control
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Conceptual Design of Boundary Layer Suction System for Energy Efficient Laminar Flow Control
Adarsh Prasannakumar (Broschiert, Englisch)
★★★★★
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Beschreibung
Hybrid Laminar Flow Control (HLFC) is one of the technologies that shows significant
drag reduction potential for the aircraft. Even though the concept of HLFC was proven
in the 1960s, a reliable, economically feasible, and energy-efficient system is still not commercially
used. One of the main reasons that restricts the use of HLFC in commercial
aviation is the complex system design, which can… lead to additional power and mass requirements.
As a solution to this problem, the thesis proposes a numerical tool for the
systematic design of a suction system for laminar flow control application. The proposed
design tool, named Actual Suction and Power Calculation Tool (ASPeCT), uses a modular
architecture and incorporates global and local level dependencies through a multi-level
input module. Three sub-routines are developed within ASPeCT to design the suction
system layout and estimate the suction power and weight requirement of the system. The
present study hypothesizes that by using the proposed suction system design tool, the actual
benefits in terms of suction power and system weight could be derived during the
conceptual design phase, leading to potential higher actual benefits and easier suction
system integration to the aircraft wing.
As a first step towards testing the hypothesis, a novel suction system concept is proposed.
The new suction system consists of a micro-perforated outer sheet supported on
an inner structure and a plenum chamber driven by the compressor. The inner structure
is composed of straight stringers with throttle holes provided on it. These throttle holes
provide additional control on the static pressure below the perforated sheet that drives
the boundary layer suction. The diameter of the throttle holes can be numerically estimated
to match any desired target suction velocity distribution based on the pressure loss
characteristics of the suction system components. A new flowbench test stand is designed
to determine these pressure loss characteristics.
Eight micro-perforated sheet samples manufactured using Stereolithography (SLA), Etching,
Micro-laser drilling, and Selective Laser Melting (SLM) are measured in the current
study. The measurement data shows a significant deviation from analytical models based
on straight cylindrical holes, especially for smaller perforation diameters in the range of
60-120 μm. Two different modelling approaches are then considered to determine the effect
of perforation shape and flow behaviour. A single-hole modelling approach is used to
study the influence of the perforation shape and size. A continuum modelling approach
based on the Bohning-Doerffer (B-D) model is used to study the effect of flow behaviour.
The single-hole modelling approach shows that the conicity of the perforation affects
the pressure loss characteristics, especially at low Reynolds numbers based on hole diameter
and velocity through the single hole. A continuum modelling approach shows
that in the Darcy regime (Re < 1), the B-D models fail to predict the pressure loss accurately.
However, in the inertial regime (Re > 1), the experimental data agrees well with the
B-D model. Wind tunnel experiments are then carried out to estimate the pressure loss
through the micro-perforated sheet when suction takes place from the boundary layer.
The measurements reveal that the shear effect of the boundary layer on the wall imparts
an additional pressure loss for the micro-perforated sheet. The original B-D model fails
to predict the additional pressure loss accurately. Therefore, new coefficients are determined
based on the curve fit of the experimental data. The present study formulates a
reduced-order model based on the Priest model as well as the B-D model to model the
ii
total pressure loss through the micro-perforated sheet accurately. A similar modelling
approach is also followed to model the pressure loss through throttle holes of the inner
structure. An inner structure with throttle hole variation similar to that expected in the
HLFC system is measured to validate the reduced-order models.
Two case studies are presented using the developed toolchain ASPeCT to showcase the
functionality. The first case study deals with the design of the suction system for the
eXtended Hybrid Laminar Flow Control (xHLFC) wing for subsonic flight conditions. The
impact of the pressure characteristics of the micro-perforated sheet and inner structure
on the total power requirement of the suction system is estimated. The case study reveals
that the micro-perforated sheet accounts for less than 5% of the total suction power. The
contribution from the inner structure is approximately 15% of the total suction power.
The remaining significant amount of the suction power is used to re-energize the sucked
air back to freestream conditions.
The second case study discusses the suction system design for swept wings at transonic
flight conditions. The suction system design is performed on an aerodynamically optimized
backward-swept wing of the SE2A mid-range aircraft for a cruise Mach number
of 0.71. Four suction panels in the spanwise direction of the wing are designed using
ASPeCT. ASPeCT predicts a maximum fuel reduction of 7% for the aircraft with the use
of the HLFC system, even accounting for the additional weight and power off-take from
the engine. Finally, the suction power of different airfoils from the final Pareto front is
compared to that of the minimum total drag airfoil selected by the aerodynamic wing
optimizer. The selection of a different airfoil based on the analysis leads to a reduction
of 1 kW in suction power for an approximately similar total drag coefficient. The lower
suction power corresponds to significant savings in compressor weight, leading to an increase
in actual benefit and energy efficiency of the aircraft. Dieses Produkt haben wir gerade leider nicht auf Lager.
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Technische Daten
Erscheinungsdatum
15.11.2025
Sprache
Englisch
EAN
9783947623976
Herausgeber
Technische Uni Braunschweig NFL
Serien- oder Bandtitel
NFL-Forschungsberichte
Sonderedition
Nein
Autor
Adarsh Prasannakumar
Seitenanzahl
163
Auflage
1
Einbandart
Broschiert
-.-
★★★★★
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